The present invention relates to a projection type automotive headlamp in which light beams from a light source is reflected by a reflector and radiated in parallel beam by passing through a projection lens and more particularly to an automotive headlamp in which a discharge-type bulb is employed as a light source.
Recently, projection type headlamps have remarkably been employed since it is compact is size and it can obtain extremely bright light distribution pattern as compared to the conventional reflection-type headlamp. Further, discharge-type bulbs having been employed in automotive lamps in view of their good luminous efficiency and desirable color spectrum, as well as their long service life.
However, a discharge bulb produces a large quantity of ultraviolet (UV) rays together with visual light rays from the discharge which takes place in the gases (mercury gas, iodide gas and xenon gas) contained in the discharge chamber of the lamp. Ultraviolet rays are believed capable of destroying protein molecules and further believed a cause of skin cancer. Furthermore, ultraviolet rays destroy resin materials. Thus, there has been a problem that the light output of the discharge bulb includes health-damaging ultraviolet rays so that it is undesirable to be subjected to illumination for long periods from such a lamp. Also, resin members in the vicinity of the discharge bulb tend to deteriorate rapidly.